Tens of thousands of people also have been affected in Croatia and Serbia, where the extreme conditions have disturbed land mines and their warning signs left over from the war.

A new wave of flooding was also threatening Serbia's largest power plant, the Nikola Tesla complex, which provides half the country's electricity, according to Reuters. Soldiers and energy workers worked through the night Sunday to build barriers of sandbags to keep the water back from the plant.

Djina Trisovic, union spokeswoman at plant operator EPS, told the news agency: "The plant should be safe now. We've done all we could. Now it's in the hands of God."

An aerial view of the Northern-Bosnian town of Brcko on Sunday.ELVIS BARUKCIC / AFP - Getty Images